Enzymes Flashcards
(19 cards)
Describe the function of enzymes.
Enzymes are biological catalysts made of proteins. They speed up reactions without being used up themselves. Some of the essential reactions they catalyze include respiration, photosynthesis, protein synthesis, and digestion.
Describe the induced fit model of enzyme action.
The induced fit model of enzyme action suggests that the enzyme’s active site is not a perfect fit for the substrate, but rather it changes shape in response to the substrate’s presence to achieve a complementary fit.
How does the lock and key model differ from the induced fit model?
The lock and key model suggests that the enzyme’s active site is a perfect fit for the substrate, like a key in a lock. In contrast, the induced fit model suggests that the enzyme’s active site changes shape to fit the substrate.
How does temperature affect enzyme activity?
If the temperature is too low, there is not enough kinetic energy for successful collisions between the enzyme and the substrate. If the temperature is too high, enzymes denature, the active site changes shape, and enzyme-substrate complexes cannot form.
How does pH affect enzyme activity?
Too high or too low a pH will interfere with the charges in the amino acids in the active site, causing the enzyme to denature.
How do substrate and enzyme concentrations affect enzyme activity?
If there is not enough substrate, the reaction will be slower due to fewer collisions between the enzyme and substrate. If there are not enough enzymes, the enzyme active sites will become saturated with substrate and unable to work any faster.
What is the role of competitive inhibitors in enzyme activity?
Competitive inhibitors are the same shape as the substrate and can bind to the active site, preventing the substrate from binding and the reaction from occurring. Adding more substrate can out-compete the inhibitor.
What is the role of non-competitive inhibitors in enzyme activity?
Non-competitive inhibitors bind to the enzyme away from the active site, causing the active site to change shape. As a result, the substrate can no longer bind, regardless of how much substrate is added.
Define the term ‘active site’ in the context of enzymes.
The active site is a part of an enzyme that attaches to a substrate to catalyze a reaction. It is specific and unique in shape due to the specific folding and bonding in the tertiary structure of the protein.
Do enzymes attach to all substrates or only to those that are complementary in shape?
Enzymes can only attach to substrates that are complementary in shape due to the specific active site.
How do enzymes lower the activation energy needed for a reaction to occur?
When enzymes attach to the substrate, they can lower the activation energy needed for the reaction to occur, and therefore speed up the reaction.
Define the ‘Lock & Key Model’ of enzyme action.
The Lock & Key Model suggests that the enzyme is like a lock and that the substrate is like a key that fits into it due to their complementarity in shape. This model suggests that the enzyme active site is a fixed shape and that due to random collision, the substrate can collide and attach to the enzyme.
Are enzymes considered globular or fibrous proteins?
Enzymes are considered globular proteins.
What stage in protein development results in a unique 3D structure held in place by hydrogen, ionic, and disulfide bonds?
The tertiary stage in protein development results in a unique 3D structure held in place by hydrogen, ionic, and disulfide bonds.
Describe the enzyme-substrate complex.
The enzyme-substrate complex is formed when an enzyme binds to its substrate. The charged groups within the active site are thought to distort the substrate and therefore lower the activation energy. The products are then released, and the enzyme active site is empty and ready to be reused.
Define the Induced Fit Model.
The Induced Fit Model suggests that the enzyme active site is induced, or slightly changes shape, to mold around the substrate. When the enzyme-substrate complex occurs, due to the enzyme molding around the substrate, it puts strain on the bonds and therefore lowers the activation energy. The products are then removed, and the enzyme active site returns to its original shape.
How does the Induced Fit Model differ from the Lock and Key Model?
The Induced Fit Model suggests that the active site changes shape and then becomes complementary in shape, whereas the Lock and Key Model suggests enzymes are a fixed shape, and the active site does not change.
Do enzymes have a specific function?
Yes, enzymes have a specific function. For example, Hexosaminidase is an enzyme present in blood that breaks down gangliosides, a type of lipid found on the cell surface of membranes of nerve cells. It does not break down other lipids.
Why does Hexosaminidase only break down gangliosides?
Hexosaminidase only breaks down gangliosides because enzymes are highly specific. They have an active site that is complementary to a specific substrate, in this case, gangliosides. This specificity is due to the unique shape and structure of the enzyme, which allows it to bind only to a specific substrate and catalyze a specific reaction.
